The present invention relates to an alternating current driven type plasma display.
Flat type (flat panel type) displays are studied in various ways as image displays that will replace cathode ray tubes (CRTS) constituting a mainstream at present. As such flat type displays, for example, there are a liquid crystal display (LCD), an electroluminescence display (ELD) and a plasma display (PDP). Of these, a plasma display has advantages that it permits a larger screen and a wider viewing angle relatively easily, that it has excellent durability against environmental factors such as temperature, magnetism and vibrations and that it has a long lifetime. It is expected that a plasma display can be applied not only to a television set of a hanging-up-on-the-wall fashion, but also to a large-scale public information terminal unit.
In the plasma display, a voltage is applied to discharge cells formed by charging discharge spaces with discharge gas consisting of a rare gas, and a phosphor layer in each discharge cell is excited with vacuum ultraviolet ray generated by glow discharge in the discharge gas to give light emission. That is, each discharge cell is driven according to a principle similar to that of a fluorescent lamp, and generally, the discharge cells are put together on the order of hundreds of thousands to constitute a display screen. The plasma display is largely classified into a direct current driven type (DC type) and an alternating current driven type (AC type) according to methods of applying a voltage to the discharge cells, and each type has advantages and disadvantages. The AC type plasma display is suitable for attaining a higher fineness, since separation walls which work to separate the discharge cells individually within a display screen can be formed, for example, in the form of stripes. Further, it has an advantage that electrodes are less worn out and have a long lifetime since the surfaces of the electrodes for discharge are covered with a dielectric layer.
FIG. 11 shows a partial schematic exploded perspective view of a typical constitution of a conventional AC type plasma display. This AC type plasma display comes under a so-called tri-electrode type, and discharging takes place mainly between a pair of sustain electrodes 512. In the AC type plasma display shown in FIG. 11, a first panel 10 corresponding to a front panel and a second panel 20 corresponding to a rear panel are bonded to each other in their circumferential portions.
The first panel 10 comprises a transparent first substrate 11, a plurality of pairs of sustain electrodes 512 made of a transparent electrically conductive material and formed on the first substrate 11 in the form of stripes, bus electrodes 13 made of a material having a lower electric resistivity than the sustain electrodes 512 and formed on the sustain electrodes 512 for decreasing the impedance of the sustain electrodes 512, a dielectric layer 14 formed on the first substrate 11 and also on the bus electrodes 13 and the sustain electrodes 512, and a protective layer 15 made of MgO and formed on the dielectric layer 14.
The second panel 20 comprises a second substrate 21, a plurality of address electrodes (also called data electrodes) 22 formed on the second substrate 21 in the form of stripes, a dielectric material layer 23 formed on the second substrate 21 and also on the address electrodes 22, insulating separation walls 24 formed in regions on the dielectric material layer 23 between neighboring address electrodes 22 and which extend in parallel with the address electrodes 22, and phosphor layers 25 which are formed on the dielectric material layer 23 and are also formed on the side walls of the separation walls 24. When the AC type plasma display is used for display in colors, each phosphor layer 25 is constituted of a red phosphor layer 25R, a green phosphor layer 25G and a blue phosphor layer 25B, and the phosphor layers 25R, 25G and 25B of these colors are formed in a predetermined order.
FIG. 11 is an exploded perspective view, and in an actual embodiment, top portions of the separation walls 24 on the second panel side are in contact with the protective layer 15 on the first panel side. A region where a pair of the sustain electrodes 512 and the address electrode 22 positioned between two of the separation walls 24 overlap corresponds to a discharge cell. A discharge gas is charged in a discharge space surrounded by mutually neighboring two separation walls 24, the phosphor layer 25 and the protective layer 15. The first panel 10 and the second panel 20 are bonded to each other with a frit glass in their circumferential portions.
The extending direction of projection image of the sustain electrodes 512 and the extending direction of projection image of the address electrodes 22 cross each other at right angles, and a region where a pair of the sustain electrodes 512 and one combination of the phosphor layers 25R, 25G and 25B for emitting light in three primary colors overlap corresponds to one pixel. Since glow discharge is caused between the sustain electrodes 512 that are forming a pair, the AC type plasma display of the above type is called xe2x80x9csurface discharge typexe2x80x9d. For example, a pulse voltage lower than the discharge start voltage of the discharge cell is applied to the address electrode 22 immediately before the application of a voltage between a pair of the sustain electrodes 512. In this case, a wall charge is accumulated in the discharge cell (selection of a discharge cell for display), and an apparent discharge start voltage decreases. Then, the discharge that has started between a pair of the sustain electrodes 512 can be sustained at a voltage lower than the discharge start voltage. In the discharge cell, the phosphor layer excited by irradiation with vacuum ultraviolet ray generated by glow discharge in the discharge gas emits light in a color characteristic of a phosphor material. Vacuum ultraviolet ray having a wavelength according to a type of the charged discharge gas is generated. Light emission of the phosphor layer 25 on the second panel 20 is viewed, for example, through the first panel 10.
Generally, the discharge gas charged in the discharge space is composed of a mixture prepared by mixing approximately 4% by volume of xenon (Xe) gas with an inert gas such as neon (Ne) gas, helium (He) gas or argon (Ar) gas. The gas mixture has a total pressure of approximately 6xc3x97104 Pa to 7xc3x97104 Pa, and the xenon (Xe) gas has a partial pressure of approximately 3xc3x97103 Pa. The distance between the sustain electrodes 512 forming each pair is approximately 100 xcexcm.
FIGS. 12A and 12B and FIGS. 13A and 13B show plane forms of a pair of conventional sustain electrodes 512. For clearly showing the electrodes in FIGS. 12A and 12B and FIGS. 13A and 13B, the electrodes are provided with slanting lines. In these Figures, further, showing of the dielectric layer 14 and the protective layer 15 is omitted.
In an example shown in FIG. 12A, a pair of the sustain electrodes 512 have a plane form consisting of two stripes and have two sides (two edges) extending straight and being opposite to each other. Each bus electrode 13 is in contact with one straightly extending side (one edge) of the sustain electrode 512. The other side (other edge) of one sustain electrode 512 forming a pair and the other side (other edge) of the other sustain electrode 512 forming the pair face each other at a constant interval (distance). For accomplishing a higher fineness of an alternating current driven type plasma display, it is required to decrease the discharge cells in size. When the discharge cells are decreased in size, however, the sustain electrodes constituted as shown in FIG. 12A have a problem that a portion of each sustain electrode that serves for discharging comes to have a smaller length.
FIG. 12B shows a plane form of one example of sustain electrodes that are formed for overcoming the above problem. A pair of such sustain electrodes 512A and 512B have a plane form consisting of two stripes, and have two sides (two edges) being opposite to each other. A bus electrode 13A or 13B is provided so as to be in contact with one straightly extending side (one edge) of the sustain electrode 512A or 512B. The other side (other edge) of one sustain electrode 512A forming a pair and the other side (other edge) of the other sustain electrode 512B forming the pair are formed in curved lines. The interval (distance) between the other sides of the sustain electrodes 512A and 512B forming a pair is constant.
In an example shown in FIG. 13A, a pair of sustain electrodes 512A and 512B have projection portions 512a and 512b having a rectangular plane form each and extending from bus electrodes 13A and 13B. In an example shown in FIG. 13B, a pair of sustain electrodes 512A and 512B have projection portions 512a and 512b having a T-letter-shaped plane form each and extending from bus electrodes 13A and 13B.
Meanwhile, in an alternating current driven type plasma display having the structure shown in FIG. 12B, as the discharge cells are decreased in size, abnormal discharge such as arc discharge or spark discharge sometimes takes place in a region where the bus electrode 13A and the sustain electrode 512B come close to each other or in a region where the bus electrode 13B and the sustain electrode 512A come close to each other. In an alternating current driven type plasma display having the structure shown in FIG. 13A or 13B, further, abnormal discharge sometimes takes place between a corner portion of the projection portion 512a constituting the sustain electrode 512A and a corner portion of the projection portion 512b constituting the sustain electrode 512B. When such abnormal discharge takes place, a current that is abnormally large as compared with general glow discharge flows, which results in destruction of an electrode structure, and the alternating current driven type plasma display is caused to decrease in display quality, reliability and lifetime. Otherwise, a portion where the abnormal discharge has taken place is deteriorated in durability for breakdown.
It is therefore an object of the present invention to provide an alternating current driven type plasma display that makes it possible to reliably prevent the occurrence of abnormal discharge.
According to a first aspect of the present invention for achieving the above object, there is provided an alternating current driven type plasma display comprising a first panel having electrode groups formed on a first substrate and a dielectric layer formed on the first substrate and on the electrode groups, and a second panel, the first and second panels being bonded to each other in their circumferential portions,
wherein each electrode group comprises;
(A) a first sustain electrode having two sides opposed to each other and extending in the form of a stripe,
(B) a second sustain electrode having two sides opposed to each other and extending in the form of a stripe,
(C) a first bus electrode that is in contact with a nearly straight one side of the first sustain electrode, and
(D) a second bus electrode that is in contact with a nearly straight one side of the second sustain electrode and is extending in parallel with the first bus electrode,
and further wherein the other side of the first sustain electrode in the form of a stripe and the other side of the second sustain electrode in the form of a stripe face each other,
at least part of the other side of the first sustain electrode in the form of a stripe and at least part of the other side of the second sustain electrode in the form of a stripe have the form of a curved line each, and
the distance between the other side of the first sustain electrode in the form of a stripe and the other side of the second sustain electrode in the form of a stripe is greater in a region where they are together close to the bus electrode than in other region.
In the plasma display according to the first aspect of the present invention, since the distance between the other side of the first sustain electrode in the form of a stripe and the other side of the second sustain electrode in the form of a stripe is arranged to be greater in a region where they are together close to the bus electrode than in other region, the occurrence of abnormal discharge between the first sustain electrode and the second bus electrode and the occurrence of abnormal discharge between the second sustain electrode and the first bus electrode can be reliably prevented.
According to a second aspect of the present invention for achieving the above object, there is provided an alternating current driven type plasma display comprising a first panel having electrode groups formed on a first substrate and a dielectric layer formed on the first substrate and on the electrode groups, and a second panel, the first and second panels being bonded to each other in their circumferential portions,
wherein each electrode group comprises;
(A) a first bus electrode,
(B) a second bus electrode extending in parallel with the first bus electrode,
(C) a first sustain electrode having a projection portion extending from the first bus electrode toward the second bus electrode, and
(D) a second sustain electrode having a projection portion extending from the second bus electrode toward the projection portion of the first sustain electrode,
and further wherein the top end portion of the projection portion of the first sustain electrode and the top end portion of the projection portion of the second sustain electrode face each other, and
the corner portions of the top end portion of the projection portion of the first sustain electrode and the corner portions of the top end portion of the projection portion of the second sustain electrode are chamfered.
In the alternating current driven type plasma display according to the second aspect of the present invention, the corner portions of the top end portion of the projection portion of the first sustain electrode and the corner portions of the top end portion of the projection portion of the second sustain electrode are chamfered, so that a kind of projections are removed from the top end portions of the projection portions. As a result, the occurrence of abnormal discharge between the projection portion of the first sustain electrode and the projection portion of the second sustain electrode can be reliably prevented.
According to a third aspect of the present invention for achieving the above object, there is provided an alternating current driven type plasma display comprising a first panel having electrode groups formed on a first substrate and a dielectric layer formed on the first substrate and on the electrode groups, and a second panel, the first and second panels being bonded to each other in their circumferential portions,
wherein each electrode group comprises;
(A) a first bus electrode,
(B) a second bus electrode extending in parallel with the first bus electrode,
(C) a first sustain electrode having a projection portion extending from the first bus electrode toward the second bus electrode, and
(D) a second sustain electrode having a projection portion extending from the second bus electrode toward the projection portion of the first sustain electrode,
and further wherein the top end portion of the projection portion of the first sustain electrode and the top end portion of the projection portion of the second sustain electrode face each other, and
the distance between the top end portion of the projection portion of the first sustain electrode and the top end portion of the projection portion of the second sustain electrode is broadened from the center of each top end portion to edge portions of each top end portion.
In the alternating current driven type plasma display according to the third aspect of the present invention, the distance between the top end portion of the projection portion of the first sustain electrode and the top end portion of the projection portion of the second sustain electrode is broadened from the center of each top end portion to the edge portions of each top end portion, so that the occurrence of abnormal discharge between the projection portion of the first sustain electrode and the projection portion of the second sustain electrode can be reliably prevented.
According to a fourth aspect of the present invention for achieving the above object, there is provided an alternating current driven type plasma display comprising a first panel having electrode groups formed on a first substrate and a dielectric layer formed on the first substrate and on the electrode groups, and a second panel, the first and second panels being bonded to each other in their circumferential portions,
wherein each electrode group comprises;
(A) a first sustain electrode having two sides opposed to each other and extending in the form of a stripe,
(B) a second sustain electrode having two sides opposed to each other and extending in the form of a stripe,
(C) a first bus electrode that is in contact with one nearly-straight side of the first sustain electrode, and
(D) a second bus electrode that is in contact with one nearly-straight side of the second sustain electrode and extending in parallel with the first bus electrode,
and further wherein the other side of the first sustain electrode in the form of a stripe and the other side of the second sustain electrode in the form of a stripe face each other,
at least part of the other side of the first sustain electrode in the form of a stripe and at least part of the other side of the second sustain electrode in the form of a stripe have the form of a curved line each,
a first discharge-inhibiting layer is formed at least in a portion of the other side of the first sustain electrode in a region where the first sustain electrode is close to the second bus electrode, and
a second discharge-inhibiting layer is formed at least in a portion of the other side of the second sustain electrode in a region where the second sustain electrode is close to the first bus electrode.
According to a fifth aspect of the present invention for achieving the above object, there is provided an alternating current driven type plasma display comprising a first panel having electrode groups formed on a first substrate and a dielectric layer formed on the first substrate and on the electrode groups, and a second panel, the first and second panels being bonded to each other in their circumferential portions,
wherein each electrode group comprises;
(A) a first bus electrode,
(B) a second bus electrode extending in parallel with the first bus electrode,
(C) a first sustain electrode having a projection portion extending from the first bus electrode toward the second bus electrode, and
(D) a second sustain electrode having a projection portion extending from the second bus electrode toward the projection portion of the first sustain electrode,
and further wherein the top end portion of the projection portion of the first sustain electrode and the top end portion of the projection portion of the second sustain electrode face each other, and
a discharge-inhibiting layer is formed on each corner portion of the top end portion of the projection portion of the first sustain electrode and on each corner portion of the top end portion of the projection portion of the second sustain electrode.
In the alternating current driven type plasma display according to the fourth or fifth aspect of the present invention, the discharge-inhibiting layer is formed, so that the occurrence of abnormal discharge between the first sustain electrode and the second bus electrode, between the second sustain electrode and the first bus electrode or between the projection portion of the first sustain electrode and the projection portion of the second sustain electrode can be reliably prevented.
In the alternating current driven type plasma display according to the first or fourth aspect of the present invention, the curved line form of at least part of the other side of the first sustain electrode and the curved line form of at least part of the other side of the second sustain electrode may be the form of any curved line or a combination of any curved lines, such as a combination of arcs, a combination of sine curves, a combination of elliptical curves, a combination of parabolas, a combination of hyperbolas, a combination of xe2x80x9cdoglegxe2x80x9d forms, a combination of xe2x80x9cSxe2x80x9d letters, a combination of at least two members selected from the group consisting of arcs, sine curves, elliptical curves, parabolas, hyperbolas, xe2x80x9cdoglegxe2x80x9d forms and xe2x80x9cSxe2x80x9d letters, a combination of a segment with a combination of arcs, sine curves, elliptical curves, parabolas, hyperbolas or xe2x80x9cdoglegxe2x80x9d forms. When the segment is further combined, desirably, the segment is arranged to be positioned in parallel with the bus electrode in a position close to the bus electrode. In view of more reliably preventing the occurrence of abnormal discharge, desirably, the curved line has no bent portion.
In the alternating current driven type plasma display according to the third aspect of the present invention, desirably, the form of the top end portion of the projection portion of the sustain electrode is the form of a moderately curved line, such as the form of an arc, a sine curve, an elliptical curve, a parabolic curve, a hyperbolic curve and the like.
In the alternating current driven type plasma display according to the first aspect of the present invention, desirably, the distance between the other side of the first sustain electrode and the other side of the second sustain electrode in a region other than the region where they are close to the bus electrode (the region which is xe2x80x9cother regionxe2x80x9d and a region that contributes to starting of glow discharge) is 1xc3x9710xe2x88x924 m or less, preferably less than 5xc3x9710xe2x88x925 m, more preferably 4xc3x9710xe2x88x925 m or less, still more preferably 2.5xc3x9710xe2x88x925 m or less. The minimum value of the distance in the above xe2x80x9cother regionxe2x80x9d can be set to be a distance in which no dielectric breakdown occurs between the first sustain electrode and the second sustain electrode. The distance between the other side of the first sustain electrode and the other side of the second sustain electrode in a region where they are close to the bus electrode can be set to have a value at which no abnormal discharge takes place between the first sustain electrode and the second bus electrode and between the second sustain electrode and the first bus electrode.
In the alternating current driven type plasma display according to the first or fourth aspect of the present invention, the embodiment in which the bus electrode is in contact with the nearly straight side of the sustain electrode includes the following embodiments:
{circle around (1)} An embodiment in which the bus electrode in the form of a stripe is formed on the sustain electrode in the vicinity of the nearly straight side of the sustain electrode;
{circle around (2)} An embodiment in which the bus electrode in the form of a stripe is formed on the sustain electrode in the vicinity of the nearly straight side of the sustain electrode, and the nearly straight side of the sustain electrode and one side of the bus electrode in the form of a stripe are in agreement; and
{circle around (3)} An embodiment in which the bus electrode in the form of a stripe is formed on the sustain electrode and is extending over the nearly straight side of the sustain electrode to reach on the first substrate.
In the alternating current driven type plasma display according to the fourth aspect of the present invention, it is sufficient that the first discharge-inhibiting layers should be formed at least in a portion of the other side of the first sustain electrode in a region where the first sustain electrode is close to the second bus electrode, and the formation of the first discharge-inhibiting layers includes the following embodiments:
{circle around (1)} An embodiment in which the first discharge-inhibiting layer is formed in a portion of the other side of the first sustain electrode in a region where the first sustain electrode is close to the second bus electrode.
{circle around (2)} An embodiment in which the first discharge-inhibiting layer is formed in a portion of the other side of the first sustain electrode and a portion of the other side of the second sustain electrode in a region where the first sustain electrode is close to the second bus electrode.
{circle around (3)} An embodiment in which the first discharge-inhibiting layer is formed from a portion of the other side of the first sustain electrode to a portion of the other side of the second sustain electrode in a region where the first sustain electrode is close to the second bus electrode.
In the alternating current driven type plasma display according to the fourth aspect of the present invention, it is sufficient that the second discharge-inhibiting layers should be formed at least in a portion of the other side of the second sustain electrode in a region where the second sustain electrode is close to the first bus electrode, and the formation of the second discharge-inhibiting layers includes the following embodiments.
{circle around (1)} An embodiment in which the second discharge-inhibiting layer is formed in a portion of the other side of the second sustain electrode in a region where the second sustain electrode is close to the first bus electrode.
{circle around (2)} An embodiment in which the second discharge-inhibiting layer is formed in a portion of the other side of the first sustain electrode and a portion of the other side of the second sustain electrode in a region where the second sustain electrode is close to the first bus electrode.
{circle around (3)} An embodiment in which the second discharge-inhibiting layer is formed from a portion of the other side of the first sustain electrode to a portion of the other side of the second sustain electrode in a region where the second sustain electrode is close to the first bus electrode.
In the alternating current driven type plasma display according to the fourth aspect of the present invention, the distance between the other side of the first sustain electrode and the other side of the second sustain electrode can be set to be 1xc3x9710xe2x88x924 m or less, preferably less than 5xc3x9710xe2x88x925 m, more preferably 4xc3x9710xe2x88x925 m or less, still more preferably 2.5xc3x9710xe2x88x925 m or less. Otherwise, the above distance may be set to be similar to the distance in the alternating current driven type plasma display according to the first aspect of the present invention. Further, the minimum value of the distance can be set to be a value at which no dielectric breakdown takes place between the first sustain electrode and the second sustain electrode.
In the alternating current driven type plasma display according to the second or fifth aspect of the present invention, the distance between the top end portion of the projection portion of the first sustain electrode and the top end portion of the projection portion of the second sustain electrode can be set to be a constant distance of 1xc3x9710xe2x88x924 m or less, preferably less than 5xc3x9710xe2x88x925 m, more preferably 4xc3x9710xe2x88x925 m or less, still more preferably 2.5xc3x9710xe2x88x925 m or less. Alternatively, in the alternating current driven type plasma display according to the fifth aspect of the present invention, the above distance may be set to be similar to the distance in the alternating current driven type plasma display according to the third aspect of the present invention. Further, the minimum value of the distance can be set to be a value at which no dielectric breakdown takes place between the top end portion of the projection portion of the first sustain electrode and the top end portion of the projection portion of the second sustain electrode.
In the alternating current driven type plasma display according to the third aspect of the present invention, the shortest distance between the top end portion of the projection portion of the first sustain electrode and the top end portion of the projection portion of the second sustain electrode can be set to be 1xc3x9710xe2x88x924 m or less, preferably less than 5xc3x9710xe2x88x925 m, more preferably 4xc3x9710xe2x88x925 m or less, still more preferably 2.5xc3x9710xe2x88x925 m or less. The minimum value of the shortest distance between the top end portion of the projection portion of the first sustain electrode and the top end portion of the projection portion of the second sustain electrode can be set to be a value at which no abnormal discharge takes place between the top end portion of the projection portion of the first sustain electrode and the top end portion of the projection portion of the second sustain electrode.
In the alternating current driven type plasma display according to any one of the first to fifth aspects of the present invention (to be abbreviated as xe2x80x9cplasma display of the present inventionxe2x80x9d hereinafter), preferably, the second panel comprises a second substrate, phosphor layers formed above the second substrate and separation walls that extend at a predetermined angle from the extending direction of the electrodes and are formed between neighboring phosphor layers.
The thus-constituted plasma display of the present invention has a structure in which the first panel and the second panel are arranged such that the dielectric layer and the phosphor layers face each other, the extending direction of the bus electrodes and the extending direction of each separation wall make a predetermined angle (for example, 90xc2x0), the space surrounded by the dielectric layer, the phosphor layer and a pair of the separation walls is charged with a rare gas, and the phosphor layer emits light by irradiation with vacuum ultraviolet ray generated, in the rare gas, on the basis of AC glow discharge that takes place between a pair of facing sustain electrodes. A region where one set of the first and second sustain electrodes and the first and second bus electrodes and a pair of the separation walls overlap corresponds to one pixel.
In the plasma display of the present invention, the rare gas charged in the space surrounded by the dielectric layer, the phosphor layer and a pair of the separation walls desirably has a pressure of from 1xc3x97102 Pa (0.001 atmospheric pressure) to 5xc3x97105 Pa (5 atmospheric pressures), preferably 1xc3x97103 Pa (0.01 atmospheric pressure) to 4xc3x97105 Pa (4 atmospheric pressures). When the distance between the other side of the first sustain electrode in the form of a stripe and the other side of the second sustain electrode in the form of a stripe is less than 5xc3x9710xe2x88x925 m, desirably, the pressure of the rare gas in the space is adjusted to 1.0xc3x97102 Pa (0.001 atmospheric pressure) to 3.0xc3x97105 Pa (3 atmospheric pressures), preferably, to 1.0xc3x97103 Pa (0.01 atmospheric pressure) to 2.0xc3x97105 Pa (2 atmospheric pressures), more preferably, to 1.0xc3x97104 Pa (0.1 atmospheric pressure) to 1.0xc3x97105 Pa (1 atmospheric pressures). In the above pressure range, the phosphor layer emits light when irradiated with vacuum ultraviolet ray generated mainly on the basis of cathode glow in the rare gas. In the above pressure range, the sputtering ratio of various members constituting the plasma display decreases with an increase in the pressure, and as a result, the lifetime of the plasma display device can be increased.
Preferably, the second electrode group constituted of a plurality of second electrodes is formed on the first substrate or the second substrate. In the former case, there can be employed a constitution in which the second electrodes are formed on an insulating layer formed on the dielectric layer and the extending direction of the second electrodes and the extending direction of the bus electrodes make a predetermined angle (for example, 90xc2x0). In the latter case, there may be employed a constitution in which the second electrodes are formed on the second substrate, the extending direction of the second electrodes and the extending direction of the bus electrodes make a predetermined angle (for example, 90xc2x0), and the phosphor layer is formed above the second electrodes.
It is preferred to employ a constitution in which the electrically conductive material constituting the first and second sustain electrodes and the electrically conductive material constituting the first and second bus electrodes differ from each other. The electrically conductive material for the first and second sustain electrodes differs depending upon whether the plasma display is a transmission type or a reflection type. In the transmission type plasma display, light emission from the phosphor layers is observed through the second panel, so that it is not any problem whether the electrically conductive material constituting the first and second sustain electrodes is transparent or non-transparent. However, the electrically conductive material constituting the second electrodes is desirably transparent when the second electrodes are formed on the second substrate. In the reflection type plasma display, light emission from the phosphor layers is observed trough the first substrate, so that it is not any problem whether the electrically conductive material constituting the second electrodes is transparent or non-transparent when the second electrodes are formed on the second substrate. However, it is desirable that the electrically conductive material constituting the first and second sustain electrodes is transparent.
The above term xe2x80x9ctransparent or non-transparentxe2x80x9d is based on the transmissivity of the electrically conductive material to light at a wavelength of emitted light (in visible light region) inhererent to phosphor materials. That is, when an electrically conductive material constituting the first and second sustain electrodes is transparent to light emitted from the phosphor layers, it can be said that the electrically conductive material is transparent. The non-transparent electrically conductive material includes Ni, Al, Au, Ag, Pd/Ag, Cr, Ta, Cu, Ba, LaB6, Ca0.2La0.8CrO3, etc., and these materials may be used alone or in combination. The transparent electrically conductive material includes ITO (indium-tin oxide) and SnO2.
The method for forming the first and second sustain electrodes can be selected from a vapor deposition method, a sputtering method, a screen printing method, a sand blasting method, a plating method or a lift-off method as required depending upon the electrically conductive material to be used. That is, the first and second sustain electrodes can be formed as first and second sustain electrodes having a predetermined pattern from the beginning by the use of a proper mask or screen, or the first and second sustain electrodes can be formed by forming an electrically conductive material layer on the entire surface and then patterning the electrically conductive material layer.
The first and second bus electrodes can be constituted, typically, of a metal material such as Ag, Al, Ni, Cu or Cr, or a stacked film such as a Cr/Cu/Cr stacked film or a Cr/Al/Cr stacked film. In the reflection type plasma display, the first and second bus electrodes made of the above metal material or the stacked film can be a factor to decrease a transmission quantity of visible light which is emitted from the phosphor layers and passes through the first substrate, so that the brightness of a display screen is decreased. It is therefore preferred to form the bus electrodes so as to be as narrow as possible so long as an electric resistance value necessary for the first and second sustain electrodes can be obtained. The method for forming the first and second bus electrodes can be selected from a vapor deposition method, a sputtering method, a screen printing method, a sand blasting method, a plating method or a lift-off method as required depending upon an electrically conductive material to be used.
In the plasma display of the present invention, since the dielectric layer is provided, the direct contact of ions and electrons to the first and second sustain electrodes can be prevented. As a result, the wearing of the first and second sustain electrodes can be prevented. The dielectric layer not only works to accumulate a wall charge, but also has functions as a resistor to limit an excess discharge current and a memory to sustain a discharge state. The material for the dielectric layer is required to be transparent when the plasma display is a reflection type, since the light emission from the phosphor layers is observed through the first substrate. The material for the dielectric layer includes, for example, a low-melting glass and silicon oxide.
In the plasma display of the present invention, desirably, a protective layer is formed on the dielectric layer. The material for the protective layer includes materials having a high secondary electron emission ratio, specifically, such as magnesium oxide (MgO), magnesium fluoride (MgF2) and calcium fluoride (CaF2). Of these, magnesium oxide is a suitable material having properties such as a high secondary electron emission ratio, a low sputtering ratio, a high light transmissivity at a wavelength of light emitted from the phosphor layers and a low discharge start voltage. The protective layer may be formed of a stacked structure composed of at least two materials selected from the group consisting of the above materials.
Preferably, the discharge-inhibiting layer is made of a material having a low secondary electron emission ratio and a high work function "PHgr" from the viewpoint that such a material causes little or no electron avalanche, emits little or no electrons and causes little or no plasma discharge. Further, desirably, the material for the discharge-inhibiting layers is a material having easy process-ability and electric insulation properties. Specific examples of the above material include various insulating materials for use in the production of semiconductor devices such as SiO2 and SiN, a glass sintered body, a combination of SiO2 and a glass sintered body, metal oxides such as Al2O3 and Cr2O3, and metal nitrides such as boron nitride (BN), tungsten nitride (WN) and aluminum nitride (AlN).
The material for the first substrate and the second substrate includes a high-distortion-point glass, soda glass (Na2O.CaO.SiO2), borosilicate glass (Na2O.B2O3.SiO2), forsterite (2MgO.SiO2) and lead glass (Na2O.PbO.SiO2). The material for the first substrate and the material for the second substrate may be the same as, or different from, each other.
The plasma display of the present invention is a so-called surface-discharge type plasma display. When the second electrode is formed on the second substrate, and when the function of the phosphor layer as a dielectric material layer is insufficient, a dielectric material layer may be formed between the second electrode group and the phosphor layer.
The phosphor layer is made of a phosphor material selected from the group consisting of a phosphor material that emits light in red, a phosphor material that emits light in green and a phosphor material that emits light in blue. The phosphor layer is formed on or above the second substrate. When the second electrode is formed on the second substrate, specifically, the phosphor layer made of a phosphor material for emitting light in red (red phosphor layer) is formed on or above the second electrode, the phosphor layer made of a phosphor material for emitting light in green (green phosphor layer) is formed on or above another second electrode, the phosphor layer made of a phosphor material for emitting light in blue (blue phosphor layer) is formed on or above still another second electrode, these phosphor layers for emitting light in three primary colors are combined to form one set, and such sets are arranged in a predetermined order. When the second electrode is formed on the first substrate, a red phosphor layer, a green phosphor layer and a blue phosphor layer are formed on the second substrate, these phosphor layers for emitting light in three primary colors are combined to form one set, and such sets are arranged in a predetermined order. A region where the first and second bus electrodes, the first and second sustain electrodes and one set of the phosphor layers for emitting light in three primary colors overlap corresponds to one pixel. The red phosphor layer, the green phosphor layer and the blue phosphor layer may be formed in the form of stripes or a grille. Further, the phosphor layer may be formed only in a region where the sustain electrode and the second electrode overlap. When the red phosphor layer, the green phosphor layer and the blue phosphor layer are formed in the form of stripes and when the second electrode is formed on the second substrate, one red phosphor layer is formed on or above one second electrode, one green phosphor layer is formed on or above one second electrode, and one blue phosphor layer is formed on or above one second electrode. When the red phosphor layer, the green phosphor layer and the blue phosphor layer are formed in the form of a grille, the red phosphor layer, the green phosphor layer and the blue phosphor layer are formed in a predetermined order on one second electrode.
When the second electrode is formed on the second substrate, the phosphor layer may be formed directly on the second electrode, or may be formed on the second electrode and also on the side walls of the separation walls. Alternatively, the phosphor layer may be formed on the dielectric material layer formed on the second electrode, or may be formed on the dielectric material layer formed on the second electrode and also on the side walls of the separation walls. Further, the phosphor layer may be formed only on the side walls of the separation walls. That xe2x80x9cthe phosphor layer is formed on or above the second electrodexe2x80x9d is a concept including all of the above-discussed embodiments in various forms.
The material for the dielectric material layer can be selected from a low-melting glass or silicon oxide, and it can be formed by a screen printing method, a sputtering method or a vacuum vapor deposition method. In some cases, a protective layer made of magnesium oxide (MgO), magnesium fluoride (MgF2) or calcium fluoride (CaF2) may be formed on the phosphor layer and/or the separation walls.
As phosphor materials for the phosphor layer, phosphor materials that have a high quantum efficiency and cause less saturation to vacuum ultraviolet ray can be selected from known phosphor materials as required. When the plasma display is intended for use as a color display, it is preferred to combine those phosphor materials which have color purities close to three primary colors defined in NTSC, which are well balanced to give white when three primary colors are mixed, which show a small afterglow time period and which can secure that the afterglow time periods of three primary colors are nearly equal. Examples of the phosphor material that emits light in red upon irradiation with vacuum ultraviolet ray include (Y2O3:Eu), (YBO3:Eu), (YVO4:Eu), (Y0.96P0.60V0.40O4:Eu0.04), [(Y,Gd)BO3:Eu], (GdBO3:Eu), (ScBO3:Eu) and (3.5MgO.0.5MgF2.GeO2:Mn). Examples of the phosphor material that emits light in green upon irradiation with vacuum ultraviolet light include (ZnSiO2:Mn), (BaAl12O19:Mn), (BaMg2Al16O27:Mn), (MgGa2O4:Mn), (YBO3:Tb), (LuBO3:Tb) and (Sr4Si3O8Cl4:Eu). Examples of the phosphor material that emits light in blue upon irradiation with vacuum ultraviolet ray include (Y2SiO5:Ce), (CaWO4:Pb), CaWO4, YP0.85V0.15O4, (BaMgAl14O23:Eu), (Sr2P2O7:Eu) and (Sr2P2O7:Sn).
The method for forming the phosphor layers includes a thick film printing method, a method in which phosphor particles are sprayed, a method in which an adhesive substance is pre-applied to a region where the phosphor layers are to be formed and phosphor particles are allowed to adhere, a method in which a photosensitive phosphor paste is provided and a phosphor layer is patterned by exposure and development, and a method in which a phosphor layer is formed on the entire surface and unnecessary portions are removed by a sand blasting method.
The separation walls may have a constitution in which they extend in parallel with the second electrodes in regions between neighboring second electrodes. That is, there may be employed a constitution in which one second electrode extends between a pair of the separation walls. In some cases, the separation walls may have a constitution in which a first separation wall extends in parallel with the bus electrodes in a region between neighboring bus electrodes and a second separation wall extends in parallel with the second electrodes in a region between neighboring second electrodes (that is, in the form of a grille). While the separation walls in the form of a grille are conventionally used in a DC driven type plasma display, they can be applied to the alternating current driven type plasma display of the present invention. The separation walls may have a meander structure.
The material for the separation wall can be selected from known insulating materials. For example, a mixture of a widely used low-melting glass with a metal oxide such as alumina can be used.
The method for forming the separation wall includes a screen printing method, a sand blasting method, a dry filming method and a photosensitive method. The above screen printing method refers to a method in which opening portions are made in those portions of a screen which correspond to portions where the separation walls are to be formed, a separation-wall-forming material on the screen is passed through the opening portions with a squeeze to form a separation-wall-forming material layer on the second substrate or the dielectric material layer (these will be generically referred to as xe2x80x9csecond substrate or the likexe2x80x9d hereinafter), and then the separation-wall-forming material layer is calcined or sintered. The above dry filming method refers to a method in which a photosensitive film is laminated on the second substrate or the like, photosensitive film on regions where the separation walls are to be formed is removed by exposure and development, opening portions formed by the removal are filled with a separation-wall-forming material and the separation-wall-forming material is calcined or sintered. The photosensitive film is combusted and removed by the calcining or sintering and the separation-wall-forming material filled in the opening portions remains to constitute the separation walls. The above photosensitive method refers to a method in which a photosensitive material layer for forming the separation walls is formed on the second substrate or the like, the material layer is patterned by exposure and development and then the patterned material layer is calcined or sintered. The above sand blasting method refers to a method in which a material layer for forming the separation walls is formed on the second substrate or the like, for example, by screen printing or with a roll coater, a doctor blade or a nozzle-ejecting coater and is dried, then, those portions in the material layer where the separation walls are to be formed are covered with a mask layer, and exposed portions of the material layer are removed by a sand blasting method. The separation walls may be formed in black to form a so-called black matrix. In this case, a high contrast of the display screen can be attained. The method of forming the black separation walls includes a method in which a light-absorbing layer such as a photosensitive silver paste layer or a low-reflection chromium layer is formed on the top portion of each separation wall and a method in which the separation walls are formed from a color resist material colored in black.
The rare gas to be charged and sealed in the space is required to satisfy the following requirements.
{circle around (1)} The rare gas is chemically stable and permits setting of a high gas pressure from the viewpoint of attaining a longer lifetime of the plasma display device;
{circle around (2)} The rare gas has a high radiation intensity of vacuum ultraviolet ray from the viewpoint of attaining a higher brightness of a display screen;
{circle around (3)} Radiated vacuum ultraviolet ray has a long wavelength from the viewpoint of increasing energy conversion efficiency from vacuum ultraviolet ray to visible light; and
{circle around (4)} The discharge start voltage is low from the viewpoint of decreasing power consumption.
As a rare gas, He (wavelength of resonance line=58.4 nm), Ne (ditto=74.4 nm), Ar (ditto=107 nm), Kr (ditto=124 nm) and Xe (ditto=147 nm) can be used alone or as mixed gases. Mixed gases are particularly useful since a decrease in the discharge start voltage based on a Penning effect can be expected. Examples of the above mixed gases include Nexe2x80x94Ar mixed gases, Hexe2x80x94Xe mixed gases and Nexe2x80x94Xe mixed gases. Of these rare gases, Xe having the longest resonance line wavelength is suitable since it also radiates intense vacuum ultraviolet ray having a wavelength of 172 nm.